Highly efficient synthesis of sucrose monolaurate by alkaline protease Protex 6L

An alkaline protease from Bacillus licheniformis, Protex 6L, was used for synthesis of sucrose monolaurate from sucrose and vinyl laurate in a tert-amyl alcohol/DMSO/water solvent mixture. Introducing sucrose as powder after mixing vinyl laurate with solvent mixture resulted in a higher reaction rate than when sucrose was added as a solution in DMSO. Response surface methodology (RSM) was applied to optimize the major reaction variables, water content, temperature and pH of the lyophilized enzyme. The optimal conditions derived from RSM (3.4% water content, 43 °C and pH of 10.1) provided a high initial reaction rate of 8.66 ± 0.3 mg/ml/h which agreed with the predicted value of 8.70 mg/ml/h. With 1.5 mg-enzyme/ml, 98.0% of the added sucrose was region-selectively converted to 1′-O-lauroylsucrose after 9 h. Under the optimized conditions, Protex 6L exhibited a higher productivity for sucrose ester synthesis than Novozym 435 and three other commonly used enzymes.

► Substrate feeding procedure affects synthesis of sucrose monolaurate by Protex 6L.
► RSM analysis was used to optimize synthesis of sucrose monolaurate by Protex 6L.
► Water content and pH of enzyme affect reaction greatly, temperature has less effect.
► Optimal condition was 3.4% water content, 43 °C and enzyme pH of 10.1.
► Under this condition, high initial reaction rate of 8.66 ± 0.3 mg/ml/h was obtained.